Connective tissue is an intimate part of all lung structures and comprises about one-fourth of the adult human lung. Abnormalities in connective tissue very quickly reflect the multiple biologic functions of lung. Earlier observations noted the isolation of dfferent proteoglycans from bronchioles, pleura and gas-exchange tissue and these proteoglycans were found to have varied biologic properties. The observations show the heterogeneity and complexity of pulmonary proteoglycan chemistry. The research program explores the nature of proteoglycans in normal lungs and the potential role of proteoglycans in the development of chronic lung diseases. As a model of human disease, experimental emphysema in rabbits will be studied with a particular emphasis on proteoglycan chemistry from different functional components of the lung. Since the primary aim of the research is to define the precise chemistry of proteoglycans in normal lung and from experimental models, these studies should show us clearly the role proteoglycans play in the pathogenesis of lung diseases.